1. Field of the Invention
The present invention relates to a printer that prints to a continuous sheet medium, and relates more particularly to a printer having a mechanism for retracting a platen from a proximal position opposite a print head in conjunction with a cover opening operation. This invention also relates to a printer for printing to continuous sheet media and single-sheet media, and relates more particularly to a printer having a diversion unit for diverting continuous sheet and single sheet media.
2. Description of the Related Art
Printers having a storage unit for internally storing a paper roll as a type of continuous sheet print medium and pulling the roll paper (i.e. paper strip) off the paper roll in the storage unit for printing are known. Printers of this type have an opening part that is opened and closed by a cover. A paper roll is typically replaced and the inside of the printer is maintained through this opening part. When a paper roll is replaced, the paper must be pulled manually from the storage unit and set into the paper transportation path, and it is therefore preferable to locate the platen and transportation rollers forming one side of the paper transportation path on the side of the cover that opens and closes the opening to the storage unit. This configuration assures that the roll paper (i.e. paper strip) can be easily aligned in the paper transportation path when the cover is opened to change the paper roll because the platen and transportation rollers retract with the cover and thus open the paper transportation path.
Printers that use a common print head to print on both continuous sheet media and single sheet forms have also become common. Printers of this type can print on single sheet forms for issuing receipts, invoices, tickets, coupons, and other such forms, and are widely used in supermarkets and retail stores. Printers of this type preferably guide both continuous sheet media and single sheet media to a common printing position, and then eject the different types of media from different exit openings after being printed. A diversion unit for diverting continuous sheet media and single sheet media to different exit paths is therefore required at a position downstream from the print head.
The platen cannot be retracted with the cover in a printer that does not have a space in the platen retraction movement direction, and the diversion unit obstructs the platen retraction movement in printers that can print on both continuous sheet media and single sheet forms. The diversion unit can also interfere with opening and closing the cover. In addition to the diversion unit obstructing smooth opening and closing of the cover in this case, damage to the diversion unit or parts on the cover side could also result.
To address this problem JP-A-2000-118064 proposes retracting the platen in conjunction with the cover while avoiding interference with the paper exit diversion unit and other parts inside the printer by adding an operation for retracting the platen from an operative position (a position closely opposite the print head) in conjunction with a cover opening action and advancing the platen to the operative position in conjunction with a cover closing action. JP-A-2000-118064 achieves this action by using a large slide mechanism in order to retract the platen from the operative position opposite the print head, and thus presents problems such as described below.
(1) The sliding resistance of the slide mechanism could obstruct smooth opening and closing of the cover.
(2) Inclusion of a large slide mechanism tends to increase the printer size.
(3) Because the slide mechanism is retracted from above the paper roll storage unit, a wide space is needed around the printer in order to open the cover wide enough to retract the slide mechanism.
The present invention is directed to solving these problems and an object of the invention is to provide a printer which can retract the platen and transportation rollers while avoiding interference with internal printer parts when opening the cover, does not obstruct smooth opening and closing of the cover, invite an increase in printer size, or require a wide space around the printer, and can accurately position the movable platen to prevent print defects and form transportation problems.
A further object of the invention is to provide a printer having a diversion unit at a position downstream from the print head for diverting continuous sheet media and single sheet media. More particularly, this printer automatically retracts the diversion unit during a cover opening operation to a position where the diversion unit will not interfere with cover opening and closing, thereby enabling a smooth cover opening operation and preventing damage to the diversion unit. This printer can also improve the operability of the cover opening operation by releasing the cover lock and retracting the diversion unit as a result of linear operation of the cover release button.
To achieve this object a printer according to the present invention has a housing (including cover and unit frame) with a paper storage unit for holding a continuous sheet medium, a cover for opening and closing an opening to the paper storage unit, a print head for printing on the continuous sheet medium pulled out from the paper storage unit, a platen pivotally supported on the cover and movable between an inoperative and an operative position relative to the cover for guiding, in its operative position, a back surface of the continuous sheet medium at a position opposite the print head, and an abutment for engaging a fixed end side of the platen and rotating the free end side of the platen in conjunction with opening and closing the cover. It is therefore possible to retract the platen together with the cover without interfering with other internal parts of the printer when the cover is opened, and unlike a conventional sliding mechanism used to advance and retract the platen, the configuration of the present invention does not interfere with smooth opening and closing of the cover, invite an increase in printer size, or require a wide space around the printer.
Furthermore, a first movable transportation roller is preferably disposed at the free end side of the platen for transporting the continuous sheet medium between the first movable transportation roller and a first fixed transportation roller disposed on the frame side. In this case the continuous sheet medium can be easily aligned to the paper transportation path when the cover is closed.
Yet further preferably, a second movable transportation roller is disposed at the fixed end side of the platen for transporting the continuous sheet medium between the second movable transportation roller and a second fixed transportation roller disposed on the frame side. Continuous sheet medium transportation problems can thus be prevented by transporting the paper with a pair of first and second transportation rollers. In addition, by holding the continuous sheet medium with the first and second movable transportation rollers when the cover is closed, appropriate tension can be applied to the continuous sheet medium and printing defects caused by slack in the continuous sheet medium can be prevented.
Yet further preferably, the first movable transportation roller contacts the first fixed transportation roller on the upstream side of the print head after the second movable transportation roller contacts the second fixed transportation roller on the downstream side of the print head when the cover is operated to close. With this configuration the first and second movable transportation rollers apply pressure to the continuous sheet medium at different times, and as a result problems such as excessive force acting on the continuous sheet medium and the transportation rollers, and applying pressure to the continuous sheet medium while there is slack in the paper, can be avoided.
Further preferably, a positioning guide part is disposed on the free end side of the platen for guiding the platen relative to the frame when the cover is operated to close. This accurately positions the platen and thus prevents printing defects and transportation problems.
Yet further preferably, the abutment substantially stops rotation of the platen near the fully closed position of the cover, and so as to allow the positioning guide part engage with a fixed guide pin on the frame side. The movable platen can thus be positioned accurately.
The guiding direction of the positioning guide part is further preferably substantially perpendicular to the direction in which the platen escapes from the print head. Movement of the platen away from the print head is thus reliably restricted by the positioning guide parts, and printing defects caused by the platen separating from the print head can be prevented.
Furthermore, because the guiding direction of the positioning guide part is substantially perpendicular to a tangent of the first movable transportation roller and the first fixed transportation roller, the first movable transportation roller can be accurately positioned to the first fixed transportation roller, and paper transportation problems due to an offset in the positions of the transportation rollers, can be prevented.
Yet further preferably, a first movable transportation roller is disposed on the free end side of the platen for transporting the continuous sheet medium between the first movable transportation roller and a first fixed transportation roller on the frame side. The support axis (shaft) of the first movable transportation roller is also positioned on the print head side of an imaginary line passing through the center of the platen and the center of first fixed transportation roller as seen in a side view. It is therefore possible to press and position the platen to the print head using the first fixed transportation roller and first movable transportation roller. The number of parts can therefore be reduced and the structure simplified compared with a configuration using special platen presser or platen positioning members.
Yet further preferably, accommodating means allowing the first movable transportation roller to pass over the first fixed transportation roller in conjunction with opening and closing the cover are provided. This reduces the load of the first movable transportation roller as it moves over the first fixed transportation roller, thus avoids deformation of or damage to members when the movable transportation roller rides over the fixed transportation roller, and avoids problems interfering with smooth opening and closing of the cover.
In one embodiment, the print head can print to continuous sheet media and a single-sheet media, and in this case the printer additionally has a diversion unit disposed at a position downstream of the print head on the frame side for diverting the continuous sheet medium and single-sheet form P2 to respective paths. The diversion unit can be retracted to a position not interfering with the opening and closing of the cover. In other words, while the diversion unit for diverting the continuous sheet medium and single-sheet form to separate exit paths is disposed at a position downstream of the print head, the diversion unit can be automatically retracted when the cover is opened or closed to a position not interfering with opening and closing the cover. Interference between the diversion unit and platen is therefore reliably avoided, the cover can be smoothly opened, and damage to the diversion unit can be avoided.
Yet further preferably the abutment is positioned near the diversion unit. In other words, by disposing the abutment near the diversion unit, which is prevented from interfering with the platen, the platen can be made as small as possible and the abutment is prevented from interfering with replacing the continuous sheet medium.
Furthermore, by disposing the second fixed transportation roller at the diversion unit and transporting the continuous sheet medium on the downstream side of the print head, slack can be prevented in the continuous sheet medium, and the medium can be reliably transported to and past the diversion unit. In addition, because the diversion unit is also used as the support member for the second fixed transportation roller, the part count can be reduced and the construction can be simplified.
Furthermore, the diversion unit is configured to pivot freely in an advancing-retracting direction relative to the continuous sheet medium transportation path or second movable transportation roller, and is urged by a presser spring in the advancing direction. The diversion unit can therefore be smoothly retracted when there is contact with the platen, and pressure can be applied reliably to the paper due to the urging force of the presser spring.
Yet further, because the diversion unit has a fixed knife for cutting the continuous sheet medium, the diversion unit is also used as the support member for the fixed knife. This further reduces the part count and simplifies the structure.
Further preferably, the printer has a cover release button disposed on the frame side and operated in a straight line, and a cover locking mechanism for locking the cover in a closed position. The cover locking mechanism enables the cover to be opened when the cover release button is operated, and thus enables the diversion unit to move to the retracted side.
The cover locking mechanism has lock pins disposed on the frame side; lock levers rotatably disposed at the frame side for engaging and releasing the lock pins; and a lock release lever rotatably disposed at the frame side. When the cover release button is operated the lock release lever moves the lock levers to disengage and release the lock pins, and move the diversion unit to the retracted side. That is, while the cover release button travels in a straight line it moves the lock levers and diversion unit by way of a pivoting lock release lever, thereby reducing the force needed to operate the cover release button and further improving the operability of the cover opening operation.
Yet further preferably, the lock release lever has a first lever part linked to the cover release button; a second lever part linked to the lock levers and the diversion unit; and a connecting part integrally linking the first and second lever parts. The first and second lever parts, are pivotally supported. This configuration increases lock release lever strength, enables the lock release lever to operate smoothly, and thus further improves the operability of the cover opening operation.
Yet further preferably, a lock release lever support part (lock release lever support member and side frame) supporting the lock release lever to pivot freely comprises a rotation support part enabling attaching the lock release lever from a lateral direction outside the normal rotation range; and a stopper limiting lateral movement of the lock release lever in the normal rotation range. Rotation of the lock release lever to outside the normal rotation range is limited by the cover release button. A special member for limiting lateral movement of the lock release lever is thus unnecessary, and the part count and the number of assembly steps can therefore be reduced and the structure can be simplified.
Further preferably, first or second lever part has a notched part contiguous to the pivot hole, and the rotation support part has a narrow part to which the notched part fits and a pivot shaft part protruding horizontally from the narrow part. The pivot hole can be fit to the pivot shaft part when the notched part is fit to the narrow part. It is therefore possible to install the lock release lever to the rotation support part using a simple configuration having a notched part formed in the lock release lever and a narrow part formed to the rotation support part.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description of a preferred embodiment taken in conjunction with the accompanying drawings.